Urbanization appears to be decreasing the number of females in some wild bee species. That's according to a study from the University of Michigan.
Researchers looked at bee populations across different landscapes, including rural and urban areas. They sampled bees from cities across Southeast Michigan, including Dexter, Ann Arbor, Ypsilanti, Dearborn, and Detroit. The researchers caught more than 3,300 bees from 143 wild bee species. Domesticated European honey bees were excluded.
As urbanization increased, species that nest in the ground had fewer females. Paul Glaum is the lead author on the study. He says the presence of pavement and impermeable surfaces can affect the nesting activities of female bees.
"What we're also seeing is that the larger landscape effect is important," Glaum said. "The physical structure, the planned structure of a landscape really matters to what kind of bees are even there to take advantage of the resources that these gardeners may be trying to provide the bee species."
Glaum says those changes could threaten bee populations because it is more difficult for male bees to find mates. It also could adversely affect pollination of plants and crops. That's because male and female bees often pollinate different plant species.
The study suggests that the effect of urbanization on wild bees has been underestimated.